1. Field of the Invention
This invention generally relates to a video or image display apparatus, and particularly relates to an apparatus designed to indicate an image represented by an input digital video signal while dividing every frame related to the video signal into a plurality of subframes.
2. Description of the Related Art
In a typical 3D (three dimensional) video or image display apparatus, a pair of 2D (two dimensional) images having a binocular parallax or disparity therebetween in the horizontal direction are indicated on a display screen as images for viewer's right and left eyes respectively. The indicated images are actually observed by a viewer via viewer's right and left eyes respectively so that the viewer can perceive a subject indicated on the display screen as stereoscopic one.
A known 3D video projection system includes two liquid-crystal projectors to indicate images for viewer's right and left eyes respectively.
Another known 3D video projection system includes a single liquid-crystal projector designed so that images for viewer's right eye and images for viewer's left eye are alternately indicated on a single screen. A viewer wears a pair of glasses with liquid crystal shutters which alternately obstruct the sights of viewer's right and left eyes so that viewer's right and left eyes are allowed to independently observe the indicated right-eye and left-eye images respectively.
Japanese patent application publication number 2009-31523 discloses a stereoscopic image display device for use with liquid-crystal shutter glasses to be worn by a viewer. The glasses have shutters for viewer's right and left eyes respectively. There can be crosstalk between images viewed by viewer's right eye and those by viewer's left eye. In Japanese application 2009-31523, timings of switching the shutters in the glasses are controlled to suppress crosstalk occurring when the frame rate is high.
Japanese patent application publication number 2012-103357 discloses a 3D video display apparatus including a single liquid-crystal projector and a drive gradation table. In Japanese application 2012-103357, every frame represented by a video signal is divided into a plurality of subframes. To suppress crosstalk, the drive gradation table is designed so that the number of active subframes for a frame increases as a gradation value of the frame rises. In some cases, transverse-direction electric fields (lateral electric fields) occur between pixels of a liquid-crystal device. It is desirable to prevent the transverse-direction electric fields from considerably deteriorating indicated images.